Directive effect of a methyl substituent in the exchange reaction of ring hydrogen with molecular deuterium in dicyclopentadienyltitanium complexes

Hydrogenated (1-methylallyl)dicyclopentadienyltitanium(III) exchanges its ring hydrogen atoms with deuterium gas. The deuterated complex can be oxidized with hydrogen chloride and air to (C₅D₅)₂TiCl₂. In the related methyl-substituted complex, obtained by hydrogenation of allylbis(methylcyclopentadienyl)titanium(III), only the ring hydrogen atoms in β-position to the methyl substituent exchanged with deuterium, the hydrogen in α-position to the substituent proved to be relatively unreactive. In the exchange reaction, an intermediate is proposed having a structure with a bridged π- as well as σ-bonded C₅H₄ or C₅H₃CH₃ group.